Otherwise, you should export the content from project 1 to a file and then import that export into project 2. Some like to use a Lagarith.avi file as the go between. For that you find, download, and install a free Lagarith video codec. When you do, it will become available for you in Premiere Elements 13/13.1 Publish+Share/Computer/AVI and Advanced Button/Video Tab for the selected preset.

Please consider, and then let us know if any of the above worked for you.